Abstract

Baseline fetal heart rate (BFHR) falls with increasing gestation age. A rise in BFHR is a recognised response to intrauterine stress. However, the normal range of BFHR is considered to be 110–160 bpm irrespective of gestation age. The authors examined the hypothesis that higher BFHR indicates intrauterine stress and will predict adverse outcome during induced labour.

The authors undertook a prospective observational study of 385 induced labours. BFHR was determined prior to induction of labour using computerised CTG (n=104) or visual inspection. Primary outcome measures were delivery by Caesarean section (CS) for suspected fetal compromise, fetal acidosis (pH<7.1), meconium stained liquor and admission to SCBU (special care baby unit). BFHR determined by computer analysis was used to determine inter-quartile ranges. All data were then analysed on the basis of these quartiles.

The IQR for BFHR were 105–130, 131–136, 137–142 and 143–160 bpm. The rates of CS for suspected fetal compromise were 10.6%, 8.4%, 11.4% and 17.1% for the first, second, third and fourth quartiles, respectively (p=0.07; fourth vs bottom three quartiles, Fisher's exact test). The rates of admission to SCBU were 3.5%, 3.6%, 3.8% and 8.1% (p=0.08; fourth vs bottom three quartiles). No trends were observed for fetal acidosis or passage of meconium.

Assessment of BFHR may be a simple tool to triage inductions into those at increased risk of CS for suspected fetal compromise and admission to SCBU necessitating inpatient induction. A larger study is underway which will be subjected to receiver-operator analysis and adjustment for confounding variables.